I'm pretty sure it was the new guest nether; I was reconstructing a house that had been griefed by multiple people and I found some grief by you. I went on to find more blocks having been changed by you (I believe the house was built by 2468avc if memory serves; I forgot to take screen shots). I did, however, notice that it seemed as though you had built some of the surrounding buildings with this other player. I think you might be right, and this may just be a misunderstanding. Can you speak to this?